1. The Field of the Invention
This invention relates to relative positioning systems, and more particularly to apparatus and methods using accelerometers to quantify changes in position.
2. The Background Art
Scuba-diving is an exhilarating and dangerous pastime. The development of underwater breathing capability (e.g. Self-Contained Underwater Breathing Apparatus or SCUBA) has opened up a new world underneath the ocean. However, a scuba diver is venturing into an alien world for which he is ill suited. In particular, determining relative position underwater presents many challenges not present when orienting oneself on land. Both ocean water and lake water typically contain quantities of particulate matter that limit visibility. In addition, water is generally impervious to radio waves. Accordingly, visual positioning techniques and radio frequency based Global Positioning System (GPS) are not available underwater. Use of magnetic compasses likewise is made impossible by the inability to take bearings from reference points due to low visibility. Relative positioning by compass also requires an individual to evaluate how far one has traveled and in what direction. However, this approach is made impossible by underwater currents. A diver carried along by a current will have an inaccurate perception of how far he or she has actually traveled.
Determining relative position underwater is extremely critical. A scuba diver in the open ocean must be able to return to the boat or be lost at sea. A diver in a cave must be able to find his or her way out. Time is also critical, inasmuch as a diver must return to a point of origin before running out of air.
Accordingly, what is needed is a relative positioning system (RPS) enabling a diver to return to a point of origin without reliance on visual or other land-oriented guidance mechanisms. Additionally, what is needed is a system able to track a divers movements and provide a trajectory pointing to a point of origin.